This section provides background information related to the present disclosure which is not necessarily prior art.
Motor bases are often used to support a drive motor coupled to an accessory, such as a heating, ventilation, and air conditioning (HVAC) unit, via a drive belt. Drive belts typically connect an output shaft of the drive motor to an input shaft of the accessory to be driven. It is well understood that the tension of the drive belt is paramount to maximize drive efficiency, reduce downtime due to maintenance and/or repair, and minimize associated maintenance requirements. It is also understood that by maintaining proper belt tension, system wear components, such as the belt itself, motor bearing, and other items, benefit from increased service life.
Determining the proper belt tension is often described as being that which is just enough to drive the maximum anticipated load without slippage. In other words, the proper belt tension can be described as the level at which one obtains maximum drive efficiency while imposing minimum stress on the belt, bearings, and components of the driven member. Presence of tension beyond this “proper belt tension” can result in unnecessary stresses imposed on the belt, bearing, and remaining components thereby resulting in premature failure. On the other hand, presence of tension below this “proper belt tension” results in belt slippage, heat, and loss of available power. The slippage and heat can unnecessary accelerate wear of the belt and pulleys.
Motor bases have been developed to permit the tension of the belt extending from the motor mounted to the motor base to the accessory to be driven to be adjusted to obtain the proper belt tension. Such motor bases can generally be described as i) fixed-position adjustable bases, which can be manually adjusted by a technician, allow adjustment by manually altering the center distance between driver and driven pulleys (or “sheaves,” for V-belt drives), or ii) automatic-position adjustable bases, which include tension-controlling bases having internal or external devices to change pulley center distance automatically as the machine runs and as load conditions require.
Unfortunately, the use of fixed adjustable bases does not permit real-time adjustment of belt tension as load varies, which can lead to increased belt wear and/or reduced available power. The alternative is to employ the automatic-position adjustable base that automatically adjusts the center distance between pulleys as load requirements demand, while the system runs.
In some previous embodiments, a motor can be bolted to the carriage, which is free to move. Turning an adjustment screw causes the follower nut, spring, and carriage to move away from the driven pulley. After the belt is installed, further screw rotation moves the carriage until the belt is snug. Continued rotation causes the follower nut to compress the spring. The spring, in turn, exerts a force on the carriage, which results in tension being applied to the belt. The force exerted by the spring equals the total tension in the belt; both forces act upon the carriage in opposite directions, and the carriage is free to move to a neutral position where all forces balance—the free body is in equilibrium.
Springs for spring-loaded bases can be sized by the manufacturer. Adjustments are made on site as the motor runs at the prevailing load. As load increases, belt tension increases until it exceeds the spring force. The spring then compresses and the carriage moves toward the driven pulley. As this happens, the increased spring force becomes equal to the increased belt tension. Whatever distance the carriage travels equals the additional distance the spring is compressed. Conversely, when belt tension decreases because the load lightens, the force of the relaxing spring moves the carriage away from the driven pulley. This results in belt tension being maintained at a value just sufficient to keep the system operating at peak efficiency—with neither slippage nor excessive tension.
However, it has been found that during maintenance periods, the use of a conventional automatic-position adjustable base may result in excessive time consumption. That is, to reduce the center distance of the system, the adjustment screw must be turned (opposite installation) to a sufficient degree to permit removal of the existing belt and installation of a new belt. Often times, it has been found that in order to avoid such tedious and time consuming operation of turning the adjustment screw (which can, in some applications, require up to 100 cycles to reduce the necessary distance), technician may attempt to pry or otherwise force removal and/or installation of belts over the pulleys. This can damage the belt and the pulleys and/or sheaves used in my applications.
Therefore, in light of the desire of maintenance companies to reduce labor charges, there exists a need in the art, as determined by applicant, to provide an automatic-position adjustable base having a quick release feature to permit the safe, quick, and convenient removal and/or installation of drive belts. Moreover, there exists a need in the art, as determined by applicant, to provide a simple and convenient method for determining the wear rate and/or degree of the drive belt, sheaves, and/or pulleys. Finally, there exists a need in the art to overcome the deficiencies of the prior art.